1. Field of the Invention
The present invention is generally directed to spectrogram processing means and, more particularly, to means for correcting image tilt or curvature in a spectrogram.
2. Description of the Prior Art
Various known devices produce spectrograms. One type of a spectrogram is one consisting of a plurality of parallel images, in the shape of parallel lines. For example, in a mass spectrometer (MS) the spectrogram is formed on a detector, e.g. a photoplate, simultaneously impingable and exposed by different ion beams. These beams expose the photoplate along parallel lines which are perpendicular to the center line, lengthwise through the spectrogram.
Although the images of the spectrogram on such a photoplate are perpendicular to the center line, lengthwise through the spectrogram, the use of a photoplate as a detector has significant disadvantages, which are discussed in U.S. Pat. No. 3,955,084, hereafter referred to as patent '084. Therein, an electro-optical detector, for use in a wide mass range mass spectrometer is described. Briefly, the function of the electro-optical detector is to replace the photoplate, as the detector, and to produce an optical spectrogram, consisting of a plurality of parallel light images.
In one embodiment of the electro-optical detector light images are produced on a light-sensitive plate 40. These images are designated by numerals 56 and 57 and are shown in FIG. 6 of patent '084. These light images are described, as being transferrable by optical fibers or rods 42 (FIG. 1) to a target 45 of a vidicon camera 46 for processing. Although the electro-optical detector, described in patent '084 overcomes most of the disadvantages of a photoplate-type detector, on which a spectrogram is produced, it exhibits one possible disadvantage, which prevents its output, i.e., the light images, from being fed directly for processing by commercially-available solid-state imaging devices, without some loss in resolution.
The light images, such as 56 and 57, though parallel to one another, are slanted or tilted, rather than being perpendicular, to the center line lengthwise through the spectrogram. This characteristic is typical of the light images produced by most known electro-optical ion detectors of mass spectrometers. Since all commercially-available solid-state imaging devices are in an orthogonal geometry, tilted images of a spectrogram are not compatible with them, unless a significant loss in resolution can be tolerated, which is clearly undesirable. The cost of developing a special-purpose solid-state imaging device capable of processing a spectrogram with tilted images has been found to be extremely high. Similar problems present themselves when attempting to process images of a spectrogram which are characterized by Berry curvature. A need therefore exists for simple means for correcting image tilt or image curvature in a spectrogram.